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Kepler Mission
imran
post Sep 24 2005, 04:23 PM
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This NASA Discovery mission is to be launched in June 2008 and will search for Earth-size and smaller planets. Launch was originally scheduled in 2007 but delayed by 8 months due to "funding constraints".

Here's the official web site:
http://www.kepler.arc.nasa.gov/
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BrianJ
post Mar 7 2009, 07:45 PM
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Congratulations on a succesful launch to everyone involved with the Kepler mission.

I have two questions which someone here may be able to enlighten me on:

1. Why wasn't an L2 orbit used (similar to the forthcoming Herschel and Planck missions)? Wouldn't an L2 orbit give a longer mission lifetime?

2. If/when an exo-planet is detected, is there any way to determine the eccentricity of it's orbit (either by Kepler or by ground based observations)?

Best regards,
Brian

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Del Palmer
post Mar 8 2009, 01:49 AM
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QUOTE (BrianJ @ Mar 7 2009, 07:45 PM) *
1. Why wasn't an L2 orbit used (similar to the forthcoming Herschel and Planck missions)? Wouldn't an L2 orbit give a longer mission lifetime?


I recall L2 being mentioned early on, but they descoped along the way in order to fit on a Delta II -- it's sobering to think Kepler was rejected four times before being accepted!
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BrianJ
post Mar 8 2009, 06:11 PM
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QUOTE (Del Palmer @ Mar 8 2009, 01:49 AM) *
I recall L2 being mentioned early on, but they descoped along the way in order to fit on a Delta II -- it's sobering to think Kepler was rejected four times before being accepted!
Thanks Del. I'm certainly glad Kepler made the cut in the end!

Some back-of-the-envelope calculations tell me that Kepler has a max. dV of ~23m/s (assuming 12kg propellant, ISP 2000Ns/kg)
From what I can find out on the web, Herschel(direct injection to L2 halo orbit) will need ~200m/s dV (inc. safety margin). So Kepler would require ~90kg of extra propellant on board to match that.

The largest component of the Herschel dV budget seems to be for correction of launcher error. So I guess it's largely down to the accuracy required for a launch to L2 halo orbit (compared to a launch to Earth-trailing heliocentric orbit).

@scalbers: Thanks so much for the link to the Kepler/Planet Detection Methods page. That makes the limitations of the different methods quite clear. I was just wondering if a system similar to the Earth/Sun were detected, could we tell whether it was a "habitable" place (low eccentricity) or being alternately roasted and frozen every orbit (high eccentricity).

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Brian
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Mongo
post Mar 8 2009, 07:53 PM
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QUOTE (BrianJ @ Mar 8 2009, 06:11 PM) *
That makes the limitations of the different methods quite clear. I was just wondering if a system similar to the Earth/Sun were detected, could we tell whether it was a "habitable" place (low eccentricity) or being alternately roasted and frozen every orbit (high eccentricity).

It would be possible to determine that a particular planet had a high-eccentricity orbit using only transit information (under certain viewing circumstances), but many high-eccentricity planets would not be recognized as such.

The time between successive planetary transits (combined with the primary star's estimated mass) determines the semi-major axis, while the total duration of the transit from first to last contact is determined by the "impact factor" (how central the transit is, relative to the stellar disk), the diameter of the stellar primary and the velocity of the planet while transiting in front of the star. So if the stellar parameters are reasonably well-known, a transit duration longer than that expected from a central transit of a low-eccentricity planet says that the planet must be slower (and hence farther from its primary) at that moment than expected at any time in a low-eccentricity orbit, and so its eccentricity must be high.

However, a transit duration less than the expected duration of a central transit and a low-eccentricity orbit means little, since the transit might be off-center or grazing, which would reduce its duration as well.
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scalbers
post Mar 8 2009, 08:53 PM
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QUOTE (Mongo @ Mar 8 2009, 07:53 PM) *
It would be possible to determine that a particular planet had a high-eccentricity orbit using only transit information (under certain viewing circumstances), but many high-eccentricity planets would not be recognized as such.

The time between successive planetary transits (combined with the primary star's estimated mass) determines the semi-major axis, while the total duration of the transit from first to last contact is determined by the "impact factor" (how central the transit is, relative to the stellar disk), the diameter of the stellar primary and the velocity of the planet while transiting in front of the star. So if the stellar parameters are reasonably well-known, a transit duration longer than that expected from a central transit of a low-eccentricity planet says that the planet must be slower (and hence farther from its primary) at that moment than expected at any time in a low-eccentricity orbit, and so its eccentricity must be high.

However, a transit duration less than the expected duration of a central transit and a low-eccentricity orbit means little, since the transit might be off-center or grazing, which would reduce its duration as well.


Perhaps in principle a transit can be determined to be off-center if we time the steepness of the light curve's descent/ascent. I'm unsure though that Kepler would have the requisite time resolution.

Brian, it looks like an Earth-Sun analogue would have a few times less radial velocity than would be needed, though one might get close if the star was near and bright with lots of photons.

Syrinx, I was at a similar launch party at CU/LASP where the mission is being controlled from. I gather most of the science activity will be at Ames.


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Posts in this topic
- imran   Kepler Mission   Sep 24 2005, 04:23 PM
- - ljk4-1   Paper: astro-ph/0512251 Date: Fri, 9 Dec 2005 16:...   Dec 12 2005, 04:02 PM
|- - ljk4-1   Astrophysics, abstract astro-ph/0601186 From: Gy...   Jan 10 2006, 03:51 PM
|- - ljk4-1   Science/Astronomy: * Close-Up on the Kepler Missi...   Jan 19 2006, 07:16 PM
- - Redstone   According to the Kepler website, which doesn't...   Mar 29 2006, 07:46 PM
|- - Toymaker   QUOTE (Redstone @ Mar 29 2006, 07:46 PM) ...   Mar 30 2006, 01:05 PM
|- - PhilHorzempa   QUOTE (Redstone @ Mar 29 2006, 04:46 PM) ...   Apr 3 2006, 08:59 PM
- - BruceMoomaw   Latest news is that the launch is currently set fo...   Mar 30 2006, 06:36 PM
- - GravityWaves   Looks like a great mission, we've got loads o...   Mar 31 2006, 02:57 AM
- - PhilHorzempa   This is targeted at those with some familiarity wi...   May 22 2006, 03:05 AM
|- - BruceMoomaw   QUOTE (PhilHorzempa @ May 22 2006, 03:05 ...   May 23 2006, 01:59 AM
- - remcook   Are there known transiting exoplanets in that piec...   May 22 2006, 09:58 AM
|- - angel1801   QUOTE (remcook @ May 22 2006, 07:28 PM) A...   May 22 2006, 02:07 PM
|- - antoniseb   QUOTE (angel1801 @ May 22 2006, 08:07 AM)...   May 22 2006, 07:02 PM
|- - scalbers   QUOTE (antoniseb @ May 22 2006, 07:02 PM)...   Mar 8 2009, 03:10 PM
- - PhilHorzempa   Here is a direct look at Kepler's FOV (Field o...   May 23 2006, 03:57 AM
|- - GravityWaves   QUOTE (PhilHorzempa @ May 23 2006, 12:57 ...   Jun 14 2008, 04:12 PM
- - ljk4-1   Systems Engineering for the Kepler Mission http:/...   May 23 2006, 03:10 PM
- - PhilHorzempa   Here is an image of a Milky Way star field in the ...   Jul 1 2006, 03:42 AM
- - AlexBlackwell   The Kepler Mission: The Search for Earth-like Plan...   Feb 7 2007, 04:49 PM
|- - ustrax   Alan Stern is not kidding around...   Jul 16 2007, 03:18 PM
- - djellison   "There's a new team in town and we don...   Jul 16 2007, 03:26 PM
|- - ustrax   QUOTE (djellison @ Jul 16 2007, 04:26 PM)...   Jul 16 2007, 03:45 PM
|- - Jim from NSF.com   QUOTE (djellison @ Jul 16 2007, 11:26 AM)...   Jul 16 2007, 05:08 PM
- - Greg Hullender   I really love the Kepler mission concept, and I...   Jul 16 2007, 03:26 PM
- - hendric   Too bad Alan wasn't around to prevent the GP-B...   Jul 17 2007, 12:33 PM
|- - djellison   QUOTE (hendric @ Jul 17 2007, 01:33 PM) 1...   Jul 17 2007, 12:51 PM
- - Jim from NSF.com   Back up Skylab, Agena Triana is some where AFP-88...   Jul 17 2007, 03:18 PM
- - edstrick   "...The Saturn V at JSC is built from parts d...   Jul 18 2007, 06:12 AM
- - djellison   This is what Wiki says: Currently there are three...   Jul 18 2007, 11:26 AM
- - stevesliva   The space station appears destined to contribute a...   Jul 18 2007, 03:46 PM
|- - Jim from NSF.com   Only 3 MPLM's the rest wasn't built   Jul 18 2007, 08:10 PM
- - PhilCo126   In which parts of the Electromagnetic spectrum are...   Aug 31 2007, 06:46 PM
|- - AlexBlackwell   QUOTE (PhilCo126 @ Aug 31 2007, 08:46 AM)...   Aug 31 2007, 06:56 PM
- - PhilCo126   Kepler mission: Work in progress http://www.ballae...   Sep 8 2007, 01:05 PM
- - Del Palmer   Just finished submitting your name for LRO? Now s...   May 5 2008, 06:51 PM
- - Greg Hullender   Another Kepler update. http://www.jpl.nasa.gov/ne...   Sep 27 2008, 06:27 PM
- - Greg Hullender   They're now showing Kepler scheduled for launc...   Oct 8 2008, 05:04 PM
- - Ron Hobbs   The NASA Launch Schedule now has the Kepler launch...   Oct 11 2008, 08:04 PM
- - Ron Hobbs   Yesterday, NASA moved the launch of Kepler back to...   Oct 15 2008, 04:06 PM
- - BPCooper   I haven't seen any posts on Kepler in a while ...   Feb 21 2009, 07:56 PM
|- - helvick   Thanks for the update Ben - much appreciated. S...   Feb 22 2009, 01:11 AM
- - Byran   I hope that Kepler would have to wait for the resu...   Feb 26 2009, 06:44 PM
- - Stu   Thanks for the link to the Kepler info Byran, fasc...   Feb 26 2009, 07:03 PM
- - Greg Hullender   Although I think this bit is worth posting, since ...   Feb 26 2009, 11:11 PM
- - kwan3217   Launch has been pushed back a day to check the Del...   Feb 27 2009, 07:28 PM
|- - BPCooper   The Delta 2 rocket with Kepler has been cleared fo...   Mar 3 2009, 12:52 AM
- - imipak   *ulp*. This is the most nervous I'm going to b...   Mar 3 2009, 08:59 PM
|- - ustrax   imipak, Kepler and its possibilites is definitily ...   Mar 4 2009, 09:57 AM
- - imipak   I hope, _hope_, /HOPE!/ that you're right....   Mar 4 2009, 08:01 PM
|- - ustrax   And how cool can it get the fact of watching the l...   Mar 4 2009, 08:09 PM
- - imipak   I'm sure there's a Portuguese equivalent o...   Mar 4 2009, 08:53 PM
|- - ustrax   Yes, I know the expression...I have chosen another...   Mar 4 2009, 09:30 PM
- - PhilCo126   Did anyone found a weblink with the dimensions of ...   Mar 5 2009, 08:42 AM
|- - ustrax   Nope...I would say 5 to 6 meters tall... Only foun...   Mar 5 2009, 11:18 AM
- - PhilCo126   Ben Cooper Launchphotography has amazing photos of...   Mar 5 2009, 03:21 PM
- - Greg Hullender   I have a "no peanuts" rule this time, th...   Mar 5 2009, 04:59 PM
|- - ustrax   If my time zone doesn't fail me there will be ...   Mar 5 2009, 05:25 PM
- - Vultur   16 hours left... fingers crossed...   Mar 6 2009, 11:33 AM
|- - ugordan   QUOTE (Vultur @ Mar 6 2009, 12:33 PM) fin...   Mar 6 2009, 12:02 PM
|- - ustrax   Great to see the attention it is getting on CNN...   Mar 6 2009, 12:42 PM
- - SpaceListener   I am trying to find out about the future position ...   Mar 6 2009, 02:43 PM
|- - HughFromAlice   QUOTE (SpaceListener @ Mar 7 2009, 12:13 ...   Mar 6 2009, 03:40 PM
|- - dmuller   Does anybody know where I can find the spice kerne...   Mar 7 2009, 01:57 PM
- - remcook   My impression was that it would move further and f...   Mar 6 2009, 02:56 PM
- - SpaceListener   Thank you HughFromAlice. Its heliocentric orbit ta...   Mar 6 2009, 05:18 PM
|- - ustrax   Man...Jon Jenkins back at BTC contagiated me with ...   Mar 6 2009, 11:10 PM
- - nprev   Great, moving words. I think all of us are pretty ...   Mar 7 2009, 12:26 AM
- - Zvezdichko   Looks like launch was successful.   Mar 7 2009, 06:07 AM
- - eoincampbell   Brilliant launch Kepler, (I'm Ecstatic) Go Fin...   Mar 7 2009, 07:26 AM
- - PhilCo126   Indeed, together with CoRoT a very interesting mi...   Mar 7 2009, 07:59 AM
- - Stu   Gorgeous launch pics by Ben Cooper... http://www....   Mar 7 2009, 01:24 PM
- - FrankB   I don't know about Corot... It seems it didn...   Mar 7 2009, 01:24 PM
- - SpaceListener   I am glad to know that the launch of Kepler was st...   Mar 7 2009, 03:19 PM
- - BrianJ   Congratulations on a succesful launch to everyone ...   Mar 7 2009, 07:45 PM
|- - Del Palmer   QUOTE (BrianJ @ Mar 7 2009, 07:45 PM) 1. ...   Mar 8 2009, 01:49 AM
|- - MahFL   We saw the launch last night in real life from our...   Mar 8 2009, 02:59 AM
||- - climber   QUOTE (MahFL @ Mar 8 2009, 03:59 AM) We s...   Mar 8 2009, 04:11 PM
|- - BrianJ   QUOTE (Del Palmer @ Mar 8 2009, 01:49 AM)...   Mar 8 2009, 06:11 PM
|- - Mongo   QUOTE (BrianJ @ Mar 8 2009, 06:11 PM) Tha...   Mar 8 2009, 07:53 PM
|- - scalbers   QUOTE (Mongo @ Mar 8 2009, 07:53 PM) It w...   Mar 8 2009, 08:53 PM
- - scalbers   Yes, the radial velocity method can determine the ...   Mar 7 2009, 08:28 PM
|- - BrianJ   QUOTE (scalbers @ Mar 7 2009, 08:28 PM) Y...   Mar 7 2009, 09:56 PM
|- - scalbers   QUOTE (BrianJ @ Mar 7 2009, 09:56 PM) Usi...   Mar 8 2009, 03:06 PM
- - belleraphon1   Congratulations to the mission launch team on this...   Mar 7 2009, 09:28 PM
- - tasp   It would not be confirmable by the 3 observation c...   Mar 8 2009, 03:34 AM
- - nprev   Considering that the Kreutz group is thought to ha...   Mar 8 2009, 06:24 AM
- - Syrinx   I made it out to the Kepler launch party here at N...   Mar 8 2009, 08:00 PM
|- - dilo   QUOTE (Syrinx @ Mar 8 2009, 09:00 PM) - W...   Mar 8 2009, 09:09 PM
- - robspace54   I am an engineer for MAG Cincinnati (formerly Cinc...   Mar 10 2009, 05:18 PM
- - PhilCo126   Talking about mission life time; there was already...   Mar 10 2009, 06:33 PM
|- - HughFromAlice   QUOTE (PhilCo126 @ Mar 11 2009, 04:03 AM)...   Mar 10 2009, 10:39 PM
|- - Hungry4info   QUOTE (HughFromAlice @ Mar 10 2009, 04:39...   Mar 10 2009, 10:46 PM
||- - AndyG   QUOTE (Hungry4info @ Mar 10 2009, 10:46 P...   Mar 11 2009, 09:32 AM
||- - HughFromAlice   QUOTE (Hungry4info @ Mar 11 2009, 08:16 A...   Mar 11 2009, 10:57 AM
|- - SpaceListener   QUOTE (HughFromAlice @ Mar 10 2009, 04:39...   Mar 11 2009, 02:22 PM
|- - dilo   SpaceListener, I hope you're jocking... If y...   Mar 11 2009, 03:50 PM
|- - djellison   QUOTE (SpaceListener @ Mar 11 2009, 02:22...   Mar 11 2009, 05:11 PM
- - PhilCo126   Correct Doug... examining the star's (periodic...   Mar 12 2009, 08:58 AM
- - siravan   QUOTE (PhilCo126 @ Mar 12 2009, 03:58 AM)...   Mar 12 2009, 11:23 AM
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